In most cases, developers don’t get to choose a user’s browser. To determine whether a particular user can work with your CSS3 application, then, you need first to detect the user’s browser — and then determine whether that browser is acceptable. Creating the code required to perform this task by hand isn’t impossible, but it can be hard.

Most developers use external styles in CSS3 to reduce the amount of work required to maintain a site. A single .CSS file contains all of the styles for the site, which means that changing a style site-wide is as simple as changing that one file (rather than each page). Because the change occurs in just one place, there isn’t any chance of missing one or more changes on individual pages.

Understanding the rules of inheritance in CSS3 helps you create interesting sites that require a minimum of maintenance. By following these rules, when maintenance is required, you normally have to make just one change, rather than changing hundreds of items individually. It pays to experiment, though, so you can understand the full effects of inheritance and the effects of using multiple styles together.